An attempt is known from German Pat. No. 844507 to provide a maximum 1.2 um thick layer of copper as a softer intermediate layer which however ensures sufficient bonding strength.
It has been found, that this copper layer is initially suitable to provide a sufficient bond between the support layer of an aluminum bearing material and the binding layer proper.
During thermal loading of the bearing, particularly in internal combustion engines, tin migrates from the anti-friction layer, which consists of PbSnCu or PbSn, into this intermediate layer of copper and forms there brittle intermetallic phases of copper/tin.
Under dynamic loading these intermetallic phases cause after a short time separation of the intermediate layer from the aluminum bearing material and therefore also the galvanically applied anti-friction layer, so that the bearing does not meet the demands placed on it. In addition, due to the migration of tin from the galvanically applied anti-friction layer of PbSnCu or PbSn, there is a considerable reduction in the corrosion resistance of the anti-friction layer.
It is known from U.S. Pat. No. 2,635,020 to provide an intermediate layer of CuZn (brass) in plain bearings with backings of steel, a support layer of bronze and a galvanically applied anti-friction layer of tin-containing alloys. It was found however, that this intermediate layer of brass prevents migration of tin from the anti-friction layer only to a relatively small degree. The same applies also to intermediate layers of brass between support layers of aluminum bearing metal and galvanically applied tin-containing anti-friction layers.